1. Field of the Invention
This invention relates to a water heating apparatus, and more particularly to a method and apparatus for heating water rapidly at low power requirement.
2. Description of the Related Art
A conventional household potable water dispenser normally takes about 7-15 minutes to heat tap water so as to form potable hot water, thereby resulting in an inefficient water heating process. If tap water is heated in the household potable water dispenser at a high power as in a factory, a power supply for supplying electricity to the dispenser will be overloaded, thereby resulting in the possibility of a fire. Accordingly, there is a need for heating water rapidly in a household potable water dispenser at low power requirement.
An object of this invention is to provide a method and apparatus for heating water rapidly at low power requirement, in which only one heating element is energized and heated at any time so as to eliminate unnecessary power consumption, thereby resulting in an efficient water heating process.
According to an aspect of this invention, a method for heating water rapidly at low power requirement includes the steps of:
(1) energizing and heating a heating element of a first heating device for a first period so that the temperature of the heating element of the first heating device rises to a first temperature;
(2) simultaneously de-energizing the heating element of the first heating device, operating a first pump in order to force cold water to flow from a first reservoir into a second reservoir via the first heating device so as to effect a heat exchange between the cold water and the heating element of the first heating device such that the cold water is heated to form warm water, and energizing and heating a heating element of a second heating device for a second period so that the temperature of the heating element of the second heating device rises to a second temperature that is higher than the first temperature; and
(3) simultaneously de-energizing the heating element of the second heating device and operating a second pump in order to force the warm water from the second reservoir into the second heating device so as to effect a heat exchange between the warm water and the heating element of the second heating device such that the warm water is heated to form hot water. Because only one of the heating elements of the first and second heating devices is energized at any time, unnecessary power consumption is eliminated, thereby resulting in an efficient water heating process.
According to another aspect of this invention, an apparatus for heating water rapidly at low power requirement includes a first reservoir for storing cold water, and a control unit. A first heating device is connected to the control unit and the first reservoir, and includes a tubular body that defines a chamber therein, a heating element that is fixed in the chamber in the first heating device, an inlet that is formed in an end of the tubular body of the first heating device and that is in fluid communication with the chamber in the first heating device and the first reservoir, and an outlet that is formed in the other end of the tubular body of the first heating device and that is in fluid communication with the chamber in the first heating device. A second reservoir is connected to the tubular body of the first heating device, and is in fluid communication with the outlet in the first heating device. A first pump, which is connected to the control unit, forces the cold water from the first reservoir into the second reservoir via the tubular body of the first heating device so as to effect a heat exchange between the cold water and the heating element of the first heating device such that the cold water is heated to form warm water. The heating element of the first heating device is energized and heated for a first period and to a first temperature just before the cold water flows into the first heating device, under control of the control unit. A second heating device is connected to the control unit and the second reservoir, and includes a tubular body that defines a chamber therein, a heating element that is fixed in the chamber in the second heating device, an inlet that is formed in an end of the tubular body of the second heating device and that is in fluid communication with the chamber in the second heating device and the second reservoir, and an outlet that is formed in the other end of the tubular body of the second heating device and that is in fluid communication with the chamber in the second heating device. The heating element of the second heating device is de-energized when the heating element of the first heating device is energized, and vice versa, under the control of the control unit. A second pump, which is connected to the control unit, forces the warm water from the second reservoir into the second heating device so as to effect a heat exchange between the warm water and the heating element of the second heating device such that the warm water is heated to form hot water. The heating element of the second heating device is energized and heated for a second period and to a second temperature, which is higher than the first temperature, just before the warm water flows into the second heating device, under the control of the control unit.